Going out to entertain Charlie is thrilling (8)
I believe the answer is:
exciting
'is thrilling' is the definition.
(similar in meaning)
'going out to entertain charlie' is the wordplay.
'going out' becomes 'exiting' ('exit' can be a synonym of 'go out').
'to entertain' indicates putting letters inside.
'charlie' becomes 'C' (phonetic alphabet).
'exiting' enclosing 'c' is 'EXCITING'.
(Other definitions for exciting that I've seen before include "moving" , "Exhilarating, stirring" , "Stirring, thrilling" , "sexy?" , "Arousing strong feeling" .)